Timing and magnitude of early Aptian extreme warming; unraveling primary δ18O variation in indurated pelagic carbonates at Deep Sea Drilling Project Site 463, central Pacific Ocean

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doi: 10.1016/j.palaeo.2007.12.007
Author(s): Ando, Atsushi; Kaiho, Kunio; Kawahata, Hodaka; Kakegawa, Takeshi
Author Affiliation(s): Primary:
Tohoku University, Institute of Geology and Paleontology, Sendai, Japan
Other:
University of Tokyo, Japan
Volume Title: Palaeogeography, Palaeoclimatology, Palaeoecology
Source: Palaeogeography, Palaeoclimatology, Palaeoecology, 260(3-4), p.463-476. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0031-0182 CODEN: PPPYAB
Note: In English. With appendix. 126 refs.; illus., incl. sects., sketch map
Summary: In order to elucidate early Aptian marine paleotemperature evolution across the period of enhanced organic carbon (Corg)-burial [Oceanic Anoxic Event (OAE) 1a], stable isotope analyses were performed on pelagic limestones at Deep Sea Drilling Project Site 463, central Pacific Ocean. The δ18O data exhibit a distinct anomaly by ∼-2 per mil spanning the OAE 1a interval (i.e., a ∼6 m-thick, phytoplanktonic Corg-rich unit constrained by magneto-, bio- and δ13C stratigraphy). Elucidation of paleotemperature significance of the δ18O shift is made by taking account of recent Sr/Ca evidence at the same section, which revealed that geochemical signals in carbonate-poor lithologies are relatively unaltered against burial diagenesis. By discriminating δ18O values from carbonate-poor samples (CaCO3 contents = 5-30 wt.%), it appears that an abrupt rise in sea-surface temperatures (SSTs) by 8°C (= -1.7 per mil shift in δ18O) occurred immediately before OAE 1a, whereas a cooling mode likely prevailed during the peak Corg-burial. In terms of its stratigraphic relationship as to the Corg-rich interval and to a pronounced negative δ13C excursion, as well as its timescale, the observed SST rise resembles those associated with the Paleocene-Eocene thermal maximum and, more strikingly, Jurassic Toarcian OAE. This observation is consistent with the hypothesis that these paleoenvironmental events were driven by a common causal mechanism, which was likely initiated by the greenhouse effect via massive release of CH4 or CO2 from the isotopically-light carbon reservoir and terminated by a negative productivity feedback. Abstract Copyright (2008) Elsevier, B.V.
Year of Publication: 2008
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Aptian; C-13/C-12; Carbon; Carbonate rocks; Central Pacific; Chronostratigraphy; Climate change; Cretaceous; DSDP Site 463; Deep Sea Drilling Project; Foraminifera; Geochemical anomalies; Geochemical profiles; Geochemistry; Greenhouse gases; IPOD; Invertebrata; Isotope ratios; Isotopes; Leg 62; Limestone; Lithostratigraphy; Lower Aptian; Lower Cretaceous; Marine environment; Mesozoic; Microfossils; O-18/O-16; OAE 1a; Oceanic anoxic events; Organic carbon; Oxygen; Pacific Ocean; Paleoclimatology; Paleotemperature; Pelagic environment; Planktonic taxa; Protista; Sea-surface temperature; Sedimentary rocks; Stable isotopes
Coordinates: N212101 N212101 E1744004 E1744004
Record ID: 2008093194
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands